Calculations Using SQL Query

Question

Hi All,
I am using Oracle Database Version 11.2.
I have a formula (A-B)/[(A-B)/10]. The tables that are holding the rows for this calculations are given below:
ROWS_TAB
====== ===================
Row          Amount
====== ===================
A            5000
B            -5000
FORMULA_TAB
======== =========== ======== =============
| ROW#  | Operator            | ROW        |   CONSTANT   |
======== =========== ======== =============
| 10        |     E                   |      A       |                         |
| 20        |     -                    |     B        |                         |
| 30        |     E                   |      A       |                         |
| 40        |     -                    |     B        |                         |
| 50        |     /                    |               |      10                |
| 60        |    /                     |               |                          |
======== =========== ======== =============
The operator E starts a new calculation. The above formula has two sub-expressions thereby the table has two rows with E. Minus denoted by -, Plus denoted by +, Multiply denoted by *, and Division denoted by /.
I want to write single SQL query to perform this calculation. Is it achievable in SQL?
The scripts used to generate the tables are as below:
create table ROWS_TAB
(row_name VARCHAR2(1),
amount NUMBER);
create table FORMULA_TAB
(row# NUMBER,
operator VARCHAR2(1),
row_name VARCHAR2(1),
constant NUMBER);
INSERT INTO ROWS_TAB VALUES('A', 5000);
INSERT INTO ROWS_TAB VALUES('B', -5000);
INSERT INTO FORMULA_TAB VALUES(10, 'E','A',null);
INSERT INTO FORMULA_TAB VALUES(20, '-','B',null);
INSERT INTO FORMULA_TAB VALUES(30, 'E','A',null);
INSERT INTO FORMULA_TAB VALUES(40, '-','B',null);
INSERT INTO FORMULA_TAB VALUES(50, '/','',10);
INSERT INTO FORMULA_TAB VALUES(60, '/','','');
Can anyone help in writing SQL query....
Thanks in advance
Best Regards
Bilal

Answer 1

As Frank said, it would be much easier to simply input the formula. Then, assuming you have OLAP option:
variable formula varchar2(30)
exec :formula := '(A-B)/((A-B)/10)';
with t as (
           select  *
             from  rows_tab
             model
               dimension by(row_number() over(order by row_name) r)
               measures(
                        row_name,
                        amount,
                        count(*) over() cnt,
                        cast(:formula as varchar2(4000)) formula
               rules(
                     formula[any] order by r = replace(nvl(formula[cv() - 1],formula[cv()]),row_name[cv()],amount[cv()])
select  :formula || ' = ' || dbms_aw.eval_number(formula) result
  from  t
  where r = cnt
RESULT
(A-B)/((A-B)/10) = 10
SQL>
And if you do not have OLAP, you could use xquery:
with t as (
           select  *
             from  rows_tab
             model
               dimension by(row_number() over(order by row_name) r)
               measures(
                        row_name,
                        amount,
                        count(*) over() cnt,
                        cast(:formula as varchar2(4000)) formula
               rules(
                     formula[any] order by r = replace(nvl(formula[cv() - 1],formula[cv()]),row_name[cv()],amount[cv()])
select  :formula || ' = ' || xmlquery(replace(formula,'/',' div ') returning content) result
  from  t
  where r = cnt
RESULT
(A-B)/((A-B)/10) = 10
SQL>
SY.